Yellow fog inhibitor



Patented June 30, 1942 OFFICE YELLOW FOG INHIBITOR Fritz Dcrsch, Binghamton, and Newton Heimbach, Johnson City, N. Y., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November-26, 1940, Serial No. 367,246

15 Claims.

halide emulsions, have a well known tendency to fog. The fog may be of two general types, namely gray fog and yellow fog. Ordinary gray fog is the more common and is caused by premature exposure, by excessive ripening of the emulsions, or by ordinary aging during storage. The socalled yellow fog, color fog, or'dichroic fog, on

" the other hand, consists essentially of a colloidal deposit of silver, the color intensity and general appearance of which are determined by the minute particle size and degree of subdivision. The fog is chiefly yellow in color and is most apparent in the lighter portions of a negative. The color may vary, however, and the colloidal silver particles may, for example, appear green by reflected light and yellow or red by transmitted light. In this case the terms color fog and dichroic fog are more applicable.

The possible causes of yellow fog are rather, numerous and may involve either the particular emulsion used or one of its constituents, or some factor in the preparation or subsequent processing of said emulsion. For example, if the developing bath contains traces of fixing solution or of excess silver halide solvent such as sulfite, or

if the developing or fixing baths are nearly exhausted, the films processed in such solutions will often show yellow fog. This fog is especially common in the handling of X-ray films which have relatively thicker emulsion layers and which are processed in partially exhausted fixing solu: tions which have been used repeatedly.

Other possible causes of yellow fog have been I discussed in the literature from time to time, and, although various remedies have been suggested, there is no well understood principle which may be said to teach the use of any general class of compounds as yellow fog inhibitors. Thus, U. S. Patent 2,059,642 suggests that a mixture of a soluble gold and mercury salts may be employed to prevent both gray and yellow fog. Furthermore, German Patent 635,605 (1936) and Photographische Korrespondenz Band 72', Seite 148 disclose the use of diphenyliodonium salts in emulsions and in developing, washing, or fixing baths as yellow fog inhibitors. Once the yellow fog has been formed, a treatment with a bath of sodium sulfide. and potassium cyanide has been suggested for its removal (Cassels Encyclopedia 55 of Photography, 1912, vol. 1, page 266). The foregoing methods cannot be considered entirely satisfactory since their use often leads'to a-loss of sensitivity, a flattening of gradation, or the formation of gray fog.

One object of our invention is to provide a new class of fog inhibiting agents which tend to prevent the' formation of yellow fog in photographic materials, without the difficulties and disadvantages of the prior art procedures.

Another object is the provision of antiyellowfog agents which may be added to a photographic emulsion or to a surface or substratum layer, without a serious decrease in the sensitivity of the emulsion.

Still another object is the provision of new yellow fog inhibitors which may be included inthe development bath itself or in a separate processing bath. Another object is the treatment of gelatines which normally cause yellow fog when used forthe manufacture of photographic emulsions, with compounds which will'decrease this tendency to fog.

' Other objects and advantages will appear from the following specification.

We have discovered that the above objects are accomplished by the use of ammonium iodides which correspond to one of the following formulas:

wherein R1, R2, R3, and R4 are separate organic roups;

represents a heterocyclic nucleus and are alkyl groups and R1 and Rs wherein Y is a member selected from the class consisting of and R is an alkyl group and Rio and R11 are members selected from the class consisting of hydrogen, alkyl, and alkoxy. The term alky as used herein has its usual significance in that it serves to designate an unsubstituted aliphatic hydrocarbon radicle.

Compounds corresponding to one of the above formulas have a definite anti-yellow fog efiect whether said compounds are incorporated in the I OH:

and N,N-dimethyl piperazin-bis-methiodide of the following formula pyridine alkiodides and their derivatives, such as pyridine ethiodide of the following formula ethiodide of the followin for- C1 5 CE Q quinoline alkiodides and their derivatives, such as quinoline ethiodide of the following formula and a-picoline mula \'I quinaldine ethiodide of the following formula- 4-ethoxyquinaldine ethiodide of the following formula CH3 and 'fi-methyl-quinoline ethiodide of the following formula In order that those persons-skilled in the art, may fully understand the nature and scope of this invention, the following specific examples are given. These examples are to be considered in an illustrative rather than a limiting sense.

Example I To one kilogram of a. light-sensitive gelatinesilver halide emulsion which ordinarily shows yellow fog, melted at 40 C., are added from 20 to 40 mg. of tetramethyl ammonium iodide. The mixture is coated on a suitable support, chilled, and dried in the usual way. This emulsion is substantially free from any tendency to exhibit yellow fog.

Example I I The tetramethyl ammonium iodide of the preceding example may be applied to the emulsion by incorporation in a surface coating.- For this use, the amount of the fog inhibitor should be chosen so that the same concentration per unit area of coated film, based on relative thickness of the surface and emulsion coatings, is employed. For instance, if the surface coating is one-tenth the thickness of the emulsion coating, approximately ten times as much tetramethyl ammoniumiodide should be used in the coating layer. In the present case this would require from 200 to. 400 mg. per kilogram of surface coating solution. The film which. carrie this coating is free from yellow fog.

Example 3 To one liter of a standard metol hydroquinone or other developer are added from 20 to 40 mg. of pyridine ethiodide. Development in this solution will avoid any fogging tendency on the part of emulsions which normally exhibit yellow fog.

Example 4 To one kilogram of a light-sensitive gelatinosilver halide emulsion as in Example I, melted at 40 C., are added from 20 to 40' mg. of trimethyl phenyl ammonium iodide. The mixture is coated on a suitable supportychilled and dried in known manner. The emulsion thus prepared is free from any substantial yellow fogging tendency.

Example 5 To one kilogram of a light-sensitive gelatinosilver halide emulsion as in Example I, melted at 40 0., are added from 10 to 50 mg. of quinaldine ethiodide. The mixture is coated, chilled and dried as above. The emulsion treated in this manner is free from yellow fog.

Example 6 To one kilogram of a light-sensitive gelatino silver halide emulsion as in Example I, melted at 4o c., are added from to so mg. of N,N'.-di-

methyl piperidinium iodide. The emulsion is pounds used may be varied slightly to suit the particular conditions involved. It is necessary however, in order to prevent yellow fog eifectively, touse amounts ranging between 10 and 50 mg. per kilogram of emulsion. Correspondingly if the compounds are added to the developer there should be used 10 to .50 mg. thereof per liter of developer.

Since these compounds tend to prevent yellow fog whether they are incorporated directly into the emulsion, added to a separate surface or substratum layer, added to the developing bath, or used in a separate processing bath, we have used the term photographic material in. the appended claims in a broad sense to include each of these applications.

Now therefore we claim: v

l. A process of preventing yellow fog in silver halide emulsions by treating the same with an organic compound selected from the class consisting of (A) Compounds corresponding to the formula R4 wherein R1, R2, R3 and R4 are separate organic groups selected from the class consisting of aryl and unsubstituted aliphatic hydrocarbon radicles; (B) Compounds corresponding to the formula R1 and Ba are unsubstituted aliphatic hydrocarbon radicles;

(C) Compounds corresponding to the formula wherein Y is a member selected from the classconsisting of nc=c11,

and

aliphatic hydrocarbon and aikoxy; said compound when present in the emulsion being incorporated in an amount of from 10 to 50' mg. per

kilogram of emulsion.

2. A photographic light-sensitive material containing as a yellow fog inhibitor for the silver halide emulsion thereof an organic compound selected from the class consisting of (A) Compounds corresponding to the.formula wherein R1, R2, R3, and are separate organic groups selected. from the class consisting of aryl and unsubstituted aliphatic wherein X represents the number of atoms necessary to complete a heterocyclic ring system and R1 andRs are unsubstituted aliphatic hydrocarbon radicles; V I

(C) Compounds corresponding to the formula wherein Y is a member selected from the class consisting of lIC=CH,

R0 is an unsubstituted aliphatic hydrocarbon group and Ru and R1; are members selected from the clas consisting of hydrogen, unsubstituted aliphatic hydrocarbon, and alkoxy; said compound when present in the emulsion being incorporated in an amount of from 10 to 50 mg. per kilogram of emulsion.

and

3. A photographic light-sensitive material containing as a yellow fog inhibitor for thesilver halideemulsion thereof an organic compound corresponding to the formula N-I I:

wherein R1, Ra, R1, and m are separate organic groups selected-from the class consisting of and and unsubstituted aliphatic hydrocarbon radicles: said compound when present in the emulsion being incorporated in an amount of from 10 to 50 mg. per kilogram of emulsion.

4. A photographic light-sensitive material containing as a yellow fog inhibitor for the silver halide emulsion thereof an organic compound corresponding to the formula hydrocarbon radwherein' R1, Ra, R3, and R4 are separate unsubstituted aliphatic hydrocarbon groups; said compound when present in the emulsion being incorporated in an amount of from to 50 mg. per kilogram of emulsion. 5. A photographic light-sensitive material containing as a yellow fog inhibitor for the silver halide emulsion thereof an organic compound corresponding to the formula wherein R1, R2, and Rsare separate unsubstituted aliphatic hydrocarbon groups and R4 is an aryl group, said compound when present in the emulsion being incorporated in an amount or from 10 to 50 mg. per kilogram of emulsion.

6. A photographic material comprising a lightsensitive gelatino silver halide emulsion layer which contains as a yellow fog inhibitor an organic compound corresponding to the formula wherein R1, R2, R3 and R4 are separate organic groups selected iron? the class consisting of aryl and unsubstituted aliphatic hydrocarbon radicles; said compound being incorporated in an amount of from 10 to 50 mg. per kilogram of emulsion.

7. Aphotographic material comprising a lightsensitive gelatinc silver halide emulsion which contains as a yellow tog inhibitor an organic compound corresponding to the formula.

iodide per kilogram of emulsion, as a yellow fog inhibiton,

10. A photographic material comprising a gelatino silver halide emulsion layer which contains as a yellow fog inhibitor an organic compound corresponding to the formula wherein R1, R2, and R3 are separate unsubstituted aliphatic hydrocarbon groups and R4 is an aryl group, said compound being incorporated in an amount of from 10 to 50 mg. per kilogram of emulsion. v

11. A photographic material comprising a gelatino silver halide emulsion which contains from 10 to 50 mg. of trimethyl phenyl ammonium iodide per kilogram of emulsion, as a yellow iog inhibitor.

12. A photographic developer comprising a developing agent and, as a yellow fog inhibitor for silver halide emulsions, an organic compound corresponding to the formula wherein R1, R2, R3 and R4 are separate organic groups selected from the class consisting of aryl and unsubstituted aliphatic hydrocarbon radicles said compound being incorporated in an amount of from 10 to 50 mg. per liter of developer. I

13. A photographic developer comprising a developing agent and tetramethyl ammonium iodide as a yellow fog inhibitor, said compound being incorporated in an amount of from 10 to 50 mg. per liter of developer.

14. A photographic developer comprising a developing agent and methyl tripropyl ammonium iodide'as a yellow fog inhibitor, said compound being incorporated in an amount of from 10 to 50 mg. per liter of developer.

15. A photographic developer comprising a developer agent and trimethyl phenyl ammonium iodide as a yellow fog inhibitor, said compound I being incorporated in an amount of from 10 to 50 mg. per liter of developer.

FRITZ DERSCH. NEWTON HEIMBACH. 

